Good Morning/Afternoon! There is a problem with the AP when I was flying from EGLL - KORD. Everytime I had the NAV mode on, it would start swaying from left to right for no reason.
It banked left and right a little bit or drastically? This could be winds, especially since you’re flying transatlantic, you’re in the jet stream and lots of turbulence will occur. A screenshot or video would really help.
This is probably because the NAV tries to get your aircraft exactly on the pink line (active leg). Sometimes it overcorrects and banks right or left to get as close to the line as possible.
EGLL to KORD, chances are you’re flying straight to the face of a 100 knots headwind from the jet stream. That’s not gonna be the smoothest ride, but without a little more information, I’m not exactly sure what can be offered, since ‘swaying side to side’ could mean various things depending on interpretation. Was it just normal turbulence? Was the AP unable to keep a course? Was the plane also porpoising? We don’t know.
If you want to share a video, that would help a lot. You can’t upload it directly, but you can upload it to YouTube then share the link here. That would help a lot.
One other question, what was your flight plan like? Was it detailed, Great Arc, style, or was it a straight shot? The shape of the Globe doesn’t easily lend itself to single-waypoint Transatlantic flights if that was the case.
Like Chris said, this being a simulator, the winds, and turbulence are included to make this realistic, but if it is a actual problem with the software, I would clear your cache, and restart the app!